The present invention relates to an image forming method, especially to an image forming method in which an image with high resolving power can be output stably by using an area gradation and an image forming apparatus using said image forming method and an image recording material.
Heretofore, the recording method is well known which comprises the step of exposing to condensed light energy such as laser beam light, etc., an image forming material, whereby a part of recording material is deformed, released, burnt or evaporated and removed. This method is a dry process in which a processing solution containing a chemical is not employed, and only the exposed portions are melt-deformed, released or evaporated, which has an advantage resulting in high contrast. This method is used for an optical recording material such as a resist material and an optical disc, a transparent image for medical diagnosis, or a transparent manuscript in making printing plate. Hereinafter, these image forming methods are defined as ablation.
Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP-A) Nos. 59-5447, 59-105638, and 62-115153 disclose an image forming method by ablation in which a binder resin is photo-degraded by a pattern exposure to form a resist and also disclose raw materials necessary to perform this method. JP-A Nos. 55-132536, 57-27788, and 57-103137 disclose a method in which a thin inorganic compound layer provided by evaporation-deposit is exposed to record information by melt-deformation. JP-A Nos. 64-56591, 1-99887, and 6-40163 disclose raw materials necessary to perform a method in which a colored binder resin is removed by light heat conversion to record information, and U.S. Pat. No. 4,245,003 disclose an image forming material comprising an image forming layer containing graphite or carbon black.
JP-A Nos.8-310124, 8-334894, 8-337053, 8-337054, 8-337055, 8-337056, 9-15849, 9-106079, and 9-226236 propose an image forming material comprising ferromagnetic powder particles as a coloring material, which are used to obtain an image with few stain and high resolving power.
However, the above mentioned image forming materials are excellent in shielding light in the region of light sensitive wavelength of printing plate as well as a transparent manuscript in making printing plate, but these image density is insufficient for a transparent image in medical diagnosis.
In cases where these image forming materials are employed for the transparent image in medical diagnosis, density gradation is required, but unevenness in a continuous gradation portion is occasionally marked depending on an exposing apparatus with these image forming materials. As a means to solve this problem, there may be a method in which the condensed light diameter of laser beam light is made small to attain high density of image element so that the resolving power is enhanced, but because an apparatus to condense light is complex, and because cost is high and exposure time is long, this method is not employed in practical use.
To overcome the above mentioned shortcomings, JP-A No. 9-109462 discloses an image forming material in which dyestuff is contained in the high density region of an image of said image forming material so as to give gradation. However, there has been a problem that a gradation changed with the passage of time with this material.
The present invention has been made to overcome the above problems. An object of the invention is to provide an image forming method in which an image density consisting of binary coding image density is enhanced and a gradation of an image consisting of binary coding image density is given, and to provide an image recording material formed by the method.